The subject matter disclosed herein relates generally to monitoring health of rotating mechanical components, and more particularly, to stall and surge detection in a compressor of a turbine.
In gas turbines used for power generation, compressors are typically allowed to operate at high pressure ratios in order to achieve higher efficiencies. During operation of a gas turbine, a phenomenon known as compressor stall may occur, when the pressure ratio of the turbine compressor exceeds a critical value at a given speed the compressor pressure ratio is reduced and the airflow that is delivered to the engine combustor is also reduced and in some circumstances may reverse direction. Compressor stalls have numerous causes. In one example, the engine is accelerated too rapidly. In another example, the inlet profile of air pressure or temperature becomes unduly distorted during normal operation of the engine. Compressor damage due to the ingestion of foreign objects or a malfunction of a portion of the engine control system may also cause a compressor stall and subsequent compressor degradation. If a compressor stall remains undetected and is permitted to continue, the combustor temperatures and the vibratory stresses induced in the compressor may become sufficiently high to cause damage to the turbine.
One approach to compressor stall detection is to monitor the health of a compressor by measuring the air flow and pressure rise through the compressor. Pressure variations may be attributed to a number of causes such as, for example, unstable combustion, rotating stall, and surge events on the compressor itself. To determine these pressure variations, the magnitude and rate of change of pressure rise through the compressor may be monitored. This approach, however, does not offer prediction capabilities of rotating stall or surge, and fails to offer information to a real-time control system with sufficient lead time to proactively deal with such events.